what did mean in extracellular and intracellular synthesis of nanop
articles
Silver nitrate and trisodium citrate were used as starting materials for the preparation of silver nanoparticles. The silver colloid was prepared by using chemical reduction method. All solutions of reacting materials were prepared in distilled water. In typical experiment 50 ml of 0.001 M AgNO3 was heated to boil. To this solution 5 mL of 1 % trisodium citrate was added drop by drop. During the process, solutions were mixed vigorously and heated until change of color was evident (pale yellow). Then it was removed from the heating device and stirred until cooled to room temperature. The mechanism of reaction could be expressed as follows:
4Ag+ + C6H5O7Na3 + 2H2O → 4Ago + C6H5O7H3 + 3Na+ + H+ + O2↑
After obtaining silver nanoparticles, the dispersion is centrifuged. Drain the solution in which there is silver nitrate and a reducing agent, add water and again centrifuge for final washing.
I would add a bit to Prof. Mirgorod answer: metal nanoparticles often tend to aggregate after centrifugation, so it may be useful to employ dialysis or ion-exchange resins instead of centrifugation. If you use excess of citrate (which is most probably), then the residual Ag+ concentration can be neglected. In this case, you can estimate the number concentration of nanoparticles after the analysis of their size distribution, assuming that all the silver nitrate was reduced to AgNP.
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